Irregular Galaxies

UGC 1597, an
irregular galaxy from the SDSS

Most galaxies fit one of the three previously described types, but
about 3% of the galaxies we observe are very different.

These so-called "irregular galaxies" do not have a lot of common features. Many of them are the
results of galaxy collisions or near misses. One type of irregular
galaxy is called a "starburst galaxy." Starburst galaxies shine
brightly as many new stars are born in a short period of time.

Irregular galaxies are usually found in groups or clusters, where
collisions and near-misses between galaxies are common. In a few
irregular galaxies, astronomers can't figure out why they look
so strange!